//
// Created by wze-zero on 2024/10/23.
//
#include <iostream>

using namespace std;

int check(int num) {
    if (num == 1) {
        return 1;
    } else if (num == 2) {
        return 2;
    } else {
        return check(num - 1) + check(num - 2);
    }
}

int main() {
    int num;
    cin >> num;
    cout << check(num) << endl;
    return 0;
}